Toner particles comprising a thermosublimable dye or pigment for use in sublimation transfer textile printing are quite well known in the art. When using said toners, the process for textile printing proceeds as follows. A toner image is formed on an intermediate substrate (e.g. paper, plastic sheet, etc.), the intermediate substrate carrying the toner image is contacted with textile and is heated for a (short) period of time. During this step the sublimable dye or pigment evaporates and enters the textile to be printed where the dye or pigment molecules diffuse into the fibre. After having the dye sublimated from the toner image to the fibres, the intermediate substrate carrying the toner image is removed. This system is especially well suited for printing on synthetic fibres, e.g. polyester.
In such a process it is important that a high amount of dye can be sublimated in a short period of time and that, during the contacting the toner image with the textile and heating it, a very low amount of toner resin is transferred to the textile. When a large amount of toner resin is transferred, the textile becomes stiff and the feel of the textile is changed at the place where the image is printed. This is quite undesirable since, especially when high-quality textiles are printed, the presence of toner resin can adversely affect the pleasure of wearing the printed textile or its draping properties.
Several propositions for toner particles comprising sublimable dye have been made for improving toner particles for use in textile printing, with toner particles containing sublimable dyes.
E.g. in U.S. Pat. No. 4,251,611 a method is described for producing single or multi-colour permanent copies by development of a latent electrostatic image, with a magnetic brush, using a toner consisting of polymer particles containing dye(s), which sublime or vaporise between 100 and 250 degrees C., and also a ferromagnetic substance. It is said that only pure dye is transferred, whilst the other components of the toner remain on the latent image and do not cause opacity or discoloration
In U.S. Pat. No. 4,391,893 spherical magnetic toner particles are prepared from a magnetic product, a polymer, and a wax. The dye used sublimates at 100-200.degree. C. and the wax is preferably a montana wax.
In U.S. Pat. No. 4,251,616, a dry electrophotographic developer consisting of a single type of particles containing an electrically conductive substance, a magnetic substance and a binder is disclosed. Typically the developer contains Carbon black (2-20%), dye(s) subliming or vaporising at 130-240 degrees C. a wax and a plasticiser. The binder is a polymer especially PVC, polystyrene or a copolymer of styrene with butadiene and an acrylic resin.
In GB-A 2,095,855 a two-component toner composition for developing latent electrostatic images is disclosed, comprising finely divided toner particles comprising a solid polymeric thermoplastic material, with a softening point (ball-ring) between 60 and 140.degree. C.; and a heat-sublimable dyestuff which sublimes at 100-220.degree. C. at atmospheric pressure and carrier particles.
In EP-A-082 163, an electrostatic single component developer is disclosed in the form of a dry fluid powder comprising spherical particles fixable by heat or pressure, comprising a binder which can be heated at 230.degree. C. without appreciable decomposition, optionally electrically conductive or very fine magnetic particles, and at least 5% of at least one sublimable or vaporisable dye which in 30 seconds at 210.degree. C. passes into the vapour state in an amt. of at least 60% at 100 hPa, whilst at atmospheric pressure under the same temperature, less than 50% passes into the vapour state in 30 seconds. The binder, having a softening point between 100 and 160.degree. C. is especially cellulose esters, vinyl resins, vinyl copolymers, polyamides or polystyrene, and containing a wax chosen from polyethylene wax, aliphatic waxes or hydroxylated fatty acids.
In EP-A-561 313 a method for textile printing is described wherein a printed pattern on transfer material is formed using pigmented powder. The transfer printing, on synthetic fabrics or similar material, proceeds by sublimation of the pigment which is a finely ground powder contained in a pulverised heat sensitive synthetic resin. The resin has a melting point around 120.degree. C.
The toner particles according to the references cited can be used for indirect textile printing, but there is still room for improvement.